How can I solve GPU rendering issue?
I think you've already identified your problem: Your card isn't officially supported. Combine that with a non official build and it's not surprising to run into errors every now and then.

You can check out the blender wiki article on AMD cards for more info: https://wiki.blender.org/index.php/OpenCL

The wiki article directly says that GCN 1.0 cards aren't supported in builds after March 2017 and that 2.78c (available form https://blender.org) should be used if you have one of those cards. It also says that the limitations are considered a TODO rather than a bug.

Basically there are known limitations with Blender's interaction with certain cards, and unfortunately you have one of them. You should definitely give the latest builds a try to see if anything has been updated, and there is a GPU+CPU option in the newest builds that might be worth checking out.